DE3532963A1 - Electrical switch - Google Patents

Abstract

An electrical switch, which is preferably provided for switching high voltage, has two erosion contact elements (6, 8) which can be engaged with one another or disengaged from one another along an axis (2). At least one of these erosion contact elements (6, 8) has, in a coaxial arrangement, a contact carrier (13, 14) extending along the axis (2) and an arc electrode (15, 16) which is mounted on the contact carrier (13, 14) and contains carbon. In the case of this switch, it is intended that the mechanical strength of the erosion contact elements be comparatively high, while maintaining low contact erosion. This is achieved in that the arc electrode (for example 15, 16) contains carbon fibres and a carbon matrix in which the carbon fibres are embedded. <IMAGE>

Description

The invention is based on an electrical Switch according to the preamble of claim 1.

With this preamble, the invention takes on one State of the art of electrical switches related, such as it is described, for example, in DE-A-25 27 326. One after state of the art electrical switch points two along an axis in or out of each other Engaging erosion contact pieces, of which at least one in a coaxial arrangement along the Axially extended contact carrier with one on the contact carrier-attached, carbon-containing electric arc trode contains. By such a carbon-containing light arc electrode is the contact erosion of the concerned Abbrandkontaktstückes compared to a metallic Ab fire contact piece reduced. The one when switching on and off mechanical switch occurring A burn-up contact piece with a carbon is able to withstand forces Arc electrode containing substance, however, only to a very limited extent to record.  

The invention as characterized in the claims is the task of an electrical switch Specify generic type, its erosion contact pieces while maintaining a low contact erosion have a high mechanical strength.

The electrical switch according to the invention stands out with low contact erosion due to a high impact strength and a pseudoplastic fracture behavior of its Burn-off contact pieces. This makes it possible to Burning contact pieces with each other at high speed to bring in or out of engagement without damage conditions of the contacted or from each other separate, arcing parts of the erosion contact pieces are to be feared.

Other features and advantages of the invention will be subsequently using one shown in the drawing and embodiments not limiting the invention explained in more detail.

Here, the only figure shows a supervision of one axially cut embodiment of a pressurized gas switches implemented and in high-voltage switchgear used electrical switch according to the invention, the status in the switch-on in the left half position and in the right half of the state during of switching off are shown.

In Fig. 1, 1 designates a substantially hollow-cylindrical formed and about consisting of Ge insulating housing. This housing 1 is filled with an insulating gas, such as sulfur hexafluoride, of a few bar pressure. It contains two switching elements 3 and 4 which can be brought into or out of engagement with one another along an axis 2 . The switching piece 3 is connected in an electrically conductive manner to a power connection (not shown) and contains a fixed nominal current contact 5 and a fixed, for example fully cylindrical, erosion contact piece 6 . The contact piece 4 is also connected in an electrically conductive manner to a further power connection, also not shown, and holds a movable nominal current contact 7 and a movable, for example hollow-cylindrical, erosion contact piece 8 . The movable rated-current contact 7 carries on a part of its inner surface an insulating nozzle 9, which is coaxial outputs the Abbrandkontaktstücke 6 and 8 in order, and which contact piece together with the movable burn-8 an annular channel 10 delimited by the turning off in a pressure gas reservoir 11 befindli ches and for example, by Arc heating or mechanical work compressed insulating gas enters the arc zone 12 (flow arrows in the right half of the figure) formed between the two erosion contact pieces 6 , 8 when switched off.

At the mutually facing and in the switch-on position (left half of the figure) in engagement with each other Lichen free ends of the erosion contacts 6 and 8 are mounted on contact carriers 13 and 14 arc electrodes 15 and 16 respectively.

The arc electrode 15 is designed as a solid cylindrical part and at least partially contains carbon fibers and a carbon matrix in which the carbon fibers are embedded. The electric arc electrode 15 has a high mechanical strength if the carbon fibers are oriented in all spatial directions or if a layer 17 of carbon fibers is wound predominantly in the circumferential direction about the axis 2 on a graphite core 18 . The arcing electrode 15 can, for example, by means of a copper and / or silver high-temperature solder with a content of between 1 and 10 percent by weight of at least one of the carbide-forming elements chromium (Co), molybdenum (Mo), tungsten (W), vanadium (V), Niobium (Nb), tantalum (Ta), titanium (Ti), zirconium (Zr), hafnium (Hf) can be attached to the contact carrier 13 . The arc electrode 15 and the contact carrier 13 can also be hollow cylindrical. In this case, the arc electrode 15 preferably contains only the layer 17 of wound carbon fibers embedded in a carbon matrix. Such layers 17 can be moved for example by winding according to the filament winding method or by winding a carbon fiber fabric.

The arc electrode 16 is ring-shaped and contains contact fingers 19 extending along the axis 2 . The contact fingers 19 also each contain carbon fibers and a carbon matrix in which the carbon fibers are embedded. Here, the carbon fibers of the contact fingers 19 are preferably at least partially radially aligned, since this results in a high electrical and thermal conductivity for the purpose of easy dissipation of the arc current and the arc heat, and a particularly high mechanical stability of the arc electrode 16 , in particular in the event of an impact during switching on the arc electrode 15 , is reached. Such radially extending carbon fibers are present, for example, in a material with three-dimensionally oriented carbon fibers, but can also be achieved by using a two-dimensional carbon fiber fabric, the first fiber direction of which is radial to the axis 2 and the second of which is axial or circumferential.

Each of the contact fingers is fastened on resilient end sections 20 of the contact carrier 14 , so that there is a good contact force between the arc electrodes 15 and 16 in the switch-on position (left half of the figure). The attachment of the contact fingers 19 can be done according to the arc electrode 15 by high temperature soldering, but can also be effected by position tion of the contact fingers 19 on paragraphs 21 , each of which is attached to one of the axis 2 facing inner surfaces of the end portions 20 of the contact carrier 14 . As indicated in the left half of the figure, a contact finger 19 can be held on one of the shoulders 21 , for example by a U-shaped leaf spring 22 , one leg of which is snapped into a recess made on the outside of one of the end sections 20 , and whose other leg engages behind the fixed erosion contact 6 free and in the direction of the axis 2 beveled end of the contact finger 19 . As indicated in the right half of the figure, the holding of a contact finger 19 on one of the shoulders 21 can also take place by means of a screw 23 which is guided approximately in the axial direction from the free end of the contact finger 19 in the shoulder 21 .

When you turn off the gas switch, the movable surface 4 is driven down by a drive, not shown. The drive can be made comparatively weak, since the frictional forces to be overcome between the two burned-in contact pieces 6 , 8 which are moved into one another in the switch-on position is low, even at high contact pressures, because of the low friction coefficient of carbon.

After opening the nominal current contact pieces 5 , 7, the current to be switched off commutates on a contact pieces 6 , 8 extending over the erosion contact current path. After separating the erosion contact pieces 6 , 8 , a switching arc is formed, the base points of which are electrodes 15 , 16 on the electric arc electrodes. Because of the comparatively high erosion resistance of carbon compared to metal electrodes, only small amounts of harmful decomposition products arise in the arcing zone 12 , whereby a deterioration in the extinguishing properties of the extinguishing gas - such as by metal vapor when using metal electrodes - is excluded. The low erosion of the carbon electrodes also enables a larger number of short-circuit shutdowns without having to overhaul the switch. When the current to be switched off approaches a zero crossing, the arc is then blown at a corresponding contact distance, as indicated by flow arrows.

When switching on, the separate fire contact pieces 6 , 8 are guided against each other by the drive, not shown. In the course of the switch-on movement, the two arc electrodes 15 , 16 can collide. Such contact bouncing is not harmful, because due to the suitable orientation of the carbon fibers, their high mechanical strength is fully effective.

Claims (7)

1. Electrical switch with two along an axis ( 2 ) with each other in or disengageable from fire contact pieces ( 6 , 8 ), of which at least one of the two erosion contact pieces ( 6 , 8 ) in coaxial arrangement Anord along the axis ( 2 ) extending contact support (13 14) and embedded a mounted on the contact carrier (13, 14), carbon-containing arc electrode (15, 16), characterized in that the arc electrode (15, 16) carbon fibers and a carbon matrix contains, in which pulp fibers coals are. 2. Switch according to claim 1, characterized in that a predominant part of the carbon fibers are mainly wound in the circumferential direction around the axis ( 2 ). 3. Switch according to claim 2, characterized in that the carbon fibers ge on a graphite core are wrapped. 4. Switch according to claim 1, characterized in that the arc electrode (z. B. 16 ) of contact fingers ( 19 ) is formed, which extends along the axis ( 2 ) on resilient end portions ( 20 ) of the contact carrier ( 16 ) attached are and have mainly carbon fibers aligned in the radial direction. 5. Switch according to claim 4, characterized in that the end sections ( 20 ) of the contact carrier ( 16 ) on their inner surface facing the axis ( 2 ) each have a shoulder ( 21 ) on which one of the contact fingers ( 19 ) is mounted . 6. Switch according to claim 5, characterized in that at least one of the contact fingers ( 19 ) is held on the shoulder ( 21 ) by means of a leaf spring ( 22 ) or a screw ( 23 ). 7. Switch according to one of claims 1-4, characterized in that the arc electrode (z. B. 15 ) with means of a copper and / or silver high temperature solder with a content of between 1 to 10 percent by weight of at least one of the carbides the elements Cr, Mo, W, V, Nb, Ta, Ti, Zr, Hf on the contact carrier (z. B. 13 ) is attached.